Enhancement mechanism of iron autotrophic denitrification system based on resource utilization of waste membranes.

Microbial-mediated iron autotrophic denitrification has gained more attention in low C/N wastewater treatment due to the organic carbon-free operation, and minimal carbon emissions. However, the selection of inexpensive iron-based electron donors, as well as the stable colonization of functional microorganisms, still restrict its application of the microbial-mediated iron autotrophic denitrification technology. In this study, we ingeniously inserted the waste iron wires into the waste membrane filaments as a component for the combination of the carrier and the electron donors. The cooperation of polyvinylidene fluoride (PVDF) membrane with microbial-mediated iron-based autotrophic denitrification were proposed to degrade nitrate nitrogen and investigate its degradation pathways. The results showed that approximately 70.0% of the nitrate was removed in the microbial mediated iron autotrophic denitrification reactor based on the resource utilization of waste membranes (Fe-PVDF-Sludge) via various removal pathway, including abiotic removal of packing materials (13.53%), heterotrophic denitrification (15.45%), and iron autotrophic denitrification (40.43%). Through the analysis of the microbial community structure of the sludge, biofilm on the surfaces of the membrane filament, and the biofilm on the surface of iron wires, a significant spatial difference was observed among different functional microorganisms. Among them, a significant enrichment of iron autotrophic denitrifiers was found to contribute 40.43% nitrate removal, and the relative abundance of autotrophic denitrifiers ranged from 2.0% to 8.01%. The integration of waste membrane filament and iron wires overcame the clogging limitations of the iron-based autotrophic denitrification technology, and achieves resource recovery from waste membrane and iron materials. This approach reduces the cost of treating micro-polluted water and demonstrates promising development prospects.